If you followed this article, you learned how to implement the IConfigurationSectionHandler interface in a custom class to store and read data on or from the app.config (or web.config) using your own typed data structure.

It is also common that you need to store a collection of values on that app.config. Example (see ProxyConfiguracionProcesos tag):

(note that the above image has been cropped to fit the space)

If that's the case, you can create a class to store a single item (in this case a "Proceso"):